1. Field of the Invention
The present invention relates to a novel discharge lamp lighting circuit, which inhibits the supply of power and a trigger pulse to a discharge lamp when an attempt is made to activate the lighting circuit while the discharge lamp is not connected to the lighting circuit.
2. Description of the Related Art
Recently, a compact discharge lamp (a metal halide lamp or the like) is receiving greater attention as a substitute light source for an incandescent lamp. It is known that a lighting circuit as adapted for a light source for a vehicular lamp, includes a DC power supply, a switching power supply circuit, a DC-AC converter, and an igniter circuit.
One known way to connect a discharge lamp to a lighting circuit is to connect a connector section of the discharge lamp to a socket which is to be connected to the output terminal of the lighting circuit, whereby power or a trigger pulse is supplied to the discharge lamp.
Since the supply voltage or trigger pulse to a discharge lamp to ignite it carries a high voltage, a high voltage is applied between connection terminals in the socket when the ignition switch is set on while the discharge lamp is not connected to the lighting circuit. If this state continues for a long period of time, the insulation of the socket may be damaged. If a worker forgets that the ignition switch has been set on and attempts to replace the discharge lamp, for example, the worker is likely to accidentally touch the connection terminals or the like of the socket and get an electric shock.